Mourners attend a funeral for men killed during battles with members of the Al Qaeda-linked Islamic State of Iraq and Syria in the northern Syrian city of Aleppo.

Mourners attend a funeral for men killed during battles with members of the Al Qaeda-linked Islamic State of Iraq and Syria in the northern Syrian city of Aleppo. (Mahmud Al-Halabi / AFP/ Getty Images)

Rebel fighters carry a man's body at the Aleppo headquarters of the Islamic State of Iraq and Syria after he was allegedly killed by the AlQaeda-linked group in January.

Rebel fighters carry a man's body at the Aleppo headquarters of the Islamic State of Iraq and Syria after he was allegedly killed by the AlQaeda-linked group in January. (Medo Halab / AFP/ Getty Images)